1. Field of the Invention
The present invention generally relates to monitoring devices and systems. More particularly, this invention relates to a child monitoring system that provides an alarm when a child has moved beyond a preset distance from a monitoring unit.
2. Description of the Prior Art
Various electronic devices have been suggested for monitoring the presence or location of persons or objects, including bracelets worn by individuals under house arrest to determine whether the individual is present in the designated house, and car chips placed in cars and used to locate the cars if stolen. An example of the former is disclosed in U.S. Pat. No. 4,736,196 to McMahon et al., and entails a band to be worn on the individual's wrist or ankle. The band houses a trigger, transmitter and antenna, with the trigger being activated by a signal from a portable control unit to operate the transmitter. When activated, the transmitter emits a signal that is detected by the control unit to verify the proximity of the band.
Significant emphasis has recently been placed on electronic systems intended to promote the safety of children, including devices worn by children to prevent their abduction. One such system is disclosed in U.S. Pat. No. 4,694,284 to Leveille et al. as consisting of a band worn by the individual being monitored. The band includes a transmitter that, upon activation of the transmitter by the wearer, broadcasts a VHF-UHF signal that can be received by a number of conventional receivers, including televisions. A drawback to this system is that a child would be required to activate the emergency signal, which may not be possible due to his or her age or under the circumstances of his or her abduction. A similar system is disclosed in U.S. Pat. No. 5,438,315 to Nix, and includes a bracelet having a transmitting unit that emits a radio signal when activated with a switch by the wearer, and a remote unit that emits an audible alarm when the radio signal is received from the bracelet. Again, required activation by the wearer can be difficult or impossible for a child.
A locating system specifically intended for children is disclosed in U.S. Pat. No. 5,617,074 to White. This system includes a receiver unit tended by an adult and a transmitting unit that is worn by a child. The transmitting unit can be turned on once the unit is appropriately fastened to the child, and then continuously emits a signal that is received and monitored by the receiving unit. Accordingly, this system is suitable for children of all ages because the wearer is not required to activate the transmitting unit in order for the system to operate as intended. The receiving unit is depicted in a drawing, but not described in any detail, as including a message receiving unit, alarms, and a distance programmer. The function of the distance programmer is not clear due to the lack of a written description of the receiving unit.
While the locating system taught by White is well suited for continuously monitoring the location of a child, improvements and additional safety features would be desirable. For example, the system disclosed by White does not include any feature that might discourage a would-be abductor from taking the child wearing the transmitting unit.